Borsh: Core Principles — Forge College

Why does Borsh matter for on-chain programs? Understanding Borsh's core principles is essential to design compact, deterministic account layouts and to interoperate reliably across languages. What you'll learn This lesson explains the concrete rules Borsh uses to turn typed data into bytes. You will learn how primitive values are encoded (integers in little-endian, booleans as one byte, raw byte arrays), how length-prefixing frames vectors and strings, and how compound values are composed from those primitives. The lesson covers canonical encoding rules for structs, enums, and Option types, and shows the decoding assumptions that require the serializer and deserializer to share type information. You will also see practical implications for on-chain data size, hashing determinism, and cross-language interop between Rust and TypeScript clients. Who this is for This is an intermediate lesson for developers familiar with basic serialization concepts and Solana account programming who want to reason about binary layouts and predictable deserialization. Key topics covered - Typed encoding: why Borsh does not include field names or runtime schema - Primitive encodings: little-endian integers, booleans, and raw bytes - Length-prefixing rules for vectors and strings - Composition rules for structs, enums, and Option types - Determinism and canonical layouts for hashing and validation - Practical implications for Solana account size and cross-language interoperability Ready to apply these rules to real account layouts and cross-client schemas? Learn more and access hands-on resources at https://www.forge.college/